You could always just grab a SATA 6Gbps PCIe card and be done with it. Small outlay to keep you happy and your system a little longer.
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PCIE x1 doesn't have the bandwith to drive sata3, does it? I doubt that would perform any better than the Marvell controller.

I think you can get some cards that are PCIe x4 which would be heaps of bandwidth. A single PCIe lane would give you 500MB/s so if your SSD is rated higher than that and the current marvel controller offers that sort of performance then a cheap expansion card would not be worth it.